The present invention concerns an aerator, more specifically an aerator capable of performing aerobic operation (aerating operation) feeding air (oxygen) into water, and anaerobic operation (agitating operation) not feeding air (oxygen) into water efficiently, by simply switching the direction of rotation of an electric motor.
Conventionally, when treating waste water by alternately switching between aerobic operation feeding air into water and anaerobic operation not feeding air into water, it was customary to install an aerator near the water surface in the sewage treating tank, and make a rotary shaft, rotatively driven by an electric motor, go up and turn in one direction to suck and splash waste water in the surrounding area like a fountain so as to perform aeration by feeding air into the water with the falling of the waste water, during an aerobic operation, but make the rotary shaft go down and turn in the opposite direction to perform agitation by producing water current in the waste water, during an anaerobic operation.
By the way, a problem with the above-described conventional aerator was that the aerator becomes complicated in structure, because, when switching between aerobic operation and anaerobic operation, it requires a lifting mechanism for lifting a rotary shaft provided with agitating blade, to suck and splash waste water in the surrounding area like a fountain, during an aerobic operation, while, on the other hand, producing water current in the waste water, during an anaerobic operation, in addition to switching the direction of rotation of the rotary shaft rotatively driven by an electric motor.
In view of said problems with conventional aerators, the objective of the present invention is to provide an aerator capable of efficiently performing both the aerobic operation of feeding air into water and the anaerobic operation of not feeding air into water, by simply switching the direction of the rotation of an electric motor, without installing any lifting mechanism to lift a rotary shaft provided with an agitating blade.
To achieve said objective, the aerator according to the present invention is an aerator provided with an agitating blade mounted on a rotary shaft driven by an electric motor, and a cylindrical body disposed in such a way to cover the area surrounding said rotary shaft, characterized in that said cylindrical body is disposed both under and above the water""s surface, and that said agitating blade is disposed by being split into an upper agitating blade for sucking up the waste water fed into the cylindrical body during an aerobic operation, and a lower agitating blade for feeding waste water into the cylindrical body during an aerobic operation, and performing agitation by producing water current in the waste water during an anaerobic operation.
This aerator, realized in such a way that a cylindrical body disposed in a way to cover the area surrounding the rotary shaft is disposed both under and above the water""s and that the agitating blade is disposed by being split into an upper agitating blade for sucking up the waste water fed into the cylindrical body during an aerobic operation, and a lower agitating blade for feeding waste water into the cylindrical body during an aerobic operation, and performing agitation by producing water current in the waste water during an anaerobic operation, feeds waste water into the cylindrical body using the upper agitating blade, by turning the rotary shaft driven by an electric motor in one direction at the start of an aerobic operation, and also sucks and splashes the waste water fed into the cylindrical body like a fountain in the surrounding area continuously thereafter, to feed air into the water so as to perform the aerobic operation of aeration during agitation, while on the other hand, producing water current in the waste water with the lower agitating blade, by turning the rotary shaft in the opposite direction during an anaerobic operation.
During this anaerobic operation, the upper agitating blade turns idly in the cylindrical body, preventing bad influences in the anaerobic operation.
In this case, said upper agitating blade may be formed in the shape of a spiral, tapered in diameter from the top toward the lower part.
This makes it possible to accurately suck up the waste water fed into the cylindrical body during an aerobic operation, and accurately prevent bad influences in anaerobic operation.
In this case, the lower part of the upper agitating blade formed in the shape of a spiral tapered in diameter from the top toward the lower part may be formed with a uniform diameter over a prescribed length in the axial direction.
This makes it possible to accurately suck up the waste water fed into the cylindrical body during an aerobic operation, without being influenced by water level fluctuations in the sewage treating tank, and more accurately prevent bad influences in anaerobic operation.
Moreover, an intermediate agitating blade may be disposed between the upper agitating blade and the lower agitating blade.
This makes it possible, during an aerobic operation, to smoothly perform the auxiliary action of feeding waste water into the cylindrical body, by means of an intermediate agitating blade.
Furthermore, the outer edge of the upper agitating blade may be formed by being bent in the direction of the rotary shaft""s rotation.
This eliminates any flow elements moving outward from the outer edge of the blade, and makes it possible to prevent the catching of impurities between the blades and the cylindrical body without reducing aerating performance, because there is no increase of water leakage from the outer edge of the blade even if you increase the gap between the blade and the cylindrical body.
Yet more, the bottom end of the rotary shaft may protrude downward from the lower agitating blade, the bottom end face being formed in the shape of an arched face.
This makes it possible, during reverse rotation of the lower agitating blade, to guide the flow of the water current, sucked upward from the bottom of the tank, smoothly toward the lower agitating blade, through the tip formed in the shape of an arched face of the shaft extending downward from the lower agitating blade, and then turn it into a current flowing upward while being agitated.
Moreover, the lower fastening plate supporting the cylindrical body and the upper fastening guide disposed above the conical guide may be connected to each other, through a stay having a blade-shaped or oval section.
This makes it possible, when waste water splashes through the gap between the lower fastening plate supporting the cylindrical body and the upper fastening guide, to extend the splashing distance, because the resistance of the splashed water can be controlled to be low with the stay having a blade-shaped or oval section.
Furthermore, the mounting angle of the stay may be adjustable.
This makes it possible to easily adjust the diffusion of waste water, depending on the shape of the tank.
Still more, the electric motor may be arranged in such a way to increase its speed at the starting time only.
This makes it possible to quickly produce an upward water current at the starting time, to stabilize the diffusion and splashing of waste water.